Device, system and method for image segmentation of an image of a scene including a subject

Abstract

The present invention relates to a device, system and method for image segmentation of an image of a scene including a subject. To improve the segmentation, the device comprises a receiver (210) configured to receive electromagnetic radiation reflected from a scene including a subject, a polarization unit (220) configured to apply a first polarization on the received electromagnetic radiation to generate first polarized radiation and to apply a second polarization, which is different from the first polarization, on the received electromagnetic radiation to generate second polarized radiation, a sensor unit (230) configured to generate a first image from the first polarized radiation and a second image from the second polarized radiation, and a segmentation unit (250) configured to identify areas of different materials in the scene from a combination of the first and second images. Further, a vital sign determination unit (240) is provided that is configured to select an area representing skin of the subject, to generate a first detection signal having a first polarization direction from the first polarized radiation in the selected area and a second detection signal having a second polarization direction, which is different from the first polarization direction, from the second polarized radiation in the selected area, and to determine a vital sign from the two detection signals by combining the two detection signals.

1 . A device for image segmentation of an image of a scene comprising a subject, said device comprising:
 a receiver for receiving electromagnetic radiation reflected from a scene comprising a subject,   a polarizer for applying a first polarization on the received electromagnetic radiation to generate a first polarized radiation and for applying a second polarization, which is different from the first polarization, on the received electromagnetic radiation to generate a second polarized radiation,   a sensor for generating a first image from the first polarized radiation and a second image from the second polarized radiation,   a segmentator for identifying areas of different materials in the scene from a combination of the first and second images, and   a vital sign determinator for:   (a) selecting an area representing skin of the subject,   (b) generating a first detection signal having a first polarization direction from the first polarized radiation in the selected area and a second detection signal having a second polarization direction, which is different from the first polarization direction, from the second polarized radiation in the selected area, and   (c) for determining a vital sign from the two detection signals by combining the two detection signals.   
     
     
         2 . The device as claimed in  claim 1 ,
 wherein said segmentator identifies areas of different materials in the scene from a ratio or difference of the first and second images.   
     
     
         3 . The device as claimed in  claim 1 ,
 wherein said sensor generates the first and second images in a single wavelength channel or in two or more different wavelength channels.   
     
     
         4 . The device as claimed in  claim 1 ,
 wherein said sensor generates the first and second images in two or more different wavelength channels; and   wherein said segmentator identifies areas of different materials in the scene from a combination of the first and second images per wavelength channel.   
     
     
         5 . The device as claimed in  claim 1 ,
 wherein said sensor generates the first and second images in two or more different wavelength channels; and   wherein said segmentator;
 (a) converts pixels of the respective first and second images into vectors with components of the two or more different wavelength channels, 
 (b) normalizes the vectors to unit length, and 
 (c) determines the cosine angle or inner product between the vectors of the two or more different wavelength channels in order to identify areas of different materials in the scene. 
   
     
     
         6 . The device as claimed in  claim 1 ,
 wherein said polarizer applies the two different polarizations simultaneously and said sensor generates the two images simultaneously.   
     
     
         7 . The device as claimed in  claim 1 ,
 wherein said polarizer applies the two different polarizations time-sequentially and said sensor unit generates the two images time-sequentially.   
     
     
         8 . The device as claimed in  claim 1 ,
 wherein said polarizer applies a first polarization which is orthogonal to the second polarization.   
     
     
         9 . The device as claimed in  claim 1 ,
 wherein said polarizer applies a first polarization which is parallel or equivalent to the polarization direction of polarized electromagnetic radiation used for illuminating the skin region of the subject and a second polarization which is orthogonal or opposite to the polarization direction of the polarized electromagnetic radiation used for illuminating the skin region of the subject.   
     
     
         10 . The device as claimed in  claim 1 ,
 wherein said vital sign determinator for determining a vital sign from the two detection signals by linearly combining the two detection signals by a weighted combination, wherein weights of said weighted combination are determined by blind signal separation and by selecting a component channel of the combined detection signals according to a predetermined criterion.   
     
     
         11 . The device as claimed in  claim 1 ,
 wherein said vital sign determinator for determining a vital sign from the two detection signals by linearly combining the two detection signals by a weighted combination using weights resulting in a pulse signal for which the products with the original detection signals equals the relative pulsatilities as represented by the respective signature vector, a signature vector providing an expected relative strength of the detection signal in the two original detection signals.   
     
     
         12 . A system for image segmentation of an image of a scene including a subject, said system comprising:
 an illuminator for illuminating a scene comprising a subject with unpolarized electromagnetic radiation or with polarized electromagnetic radiation, and   the device as claimed in  claim 1  for image segmentation of an image of the illuminated scene.   
     
     
         13 . A method for image segmentation of an image of a scene including a subject, said method comprising:
 receiving electromagnetic radiation reflected from a scene including a subject,   applying a first polarization on the received electromagnetic radiation to generate first polarized radiation and to apply a second polarization, which is different from the first polarization, on the received electromagnetic radiation to generate second polarized radiation,   generating a first image from the first polarized radiation and a second image from the second polarized radiation,   identifying areas of different materials in the scene from a combination of the first and second images,   selecting an area representing skin of the subject,   generating a first detection signal having a first polarization direction from the first polarized radiation in the selected area and a second detection signal having a second polarization direction, which is different from the first polarization direction, from the second polarized radiation in the selected area, and   determining a vital sign from the two detection signals by combining the two detection signals.   
     
     
         14 . The device of  claim 7 , wherein said polarizer applies the two different polarizations time-sequentially to alternate the polarization direction in time. 
     
     
         15 . The device of  claim 10 , wherein said weights of said weighted combination are determined by principal component analysis or independent component analysis.